CF, when you have an aircraft full of people going for a chavtastic holiday to the Costa del Plonker you can be sure that there will be a heck of a lot of people who are half canned yelling to their mates that they are at "X" altitude over somewhere, you'll have blokes yelling at their woman to get off the phone because it costs too much, kids playing with the ringtones so they are kept amused, others talking about business deals (or pretending to), etc, etc, etc.
As there will be a load of people using their phones on any given flight, plus the ambient noise, they will all get louder and louder. Think about what it can be like on a train, and then multiply it. You can be sure that someone will kick things off because of someone else using their phone, and all it needs is one nervous pax to be the one who is stressed like a piano wire and having to suffer someone gabbling away on his cellphone and you have a situation.....